Exhaust silencer

ABSTRACT

An exhaust silencer has an inner, flexible pipe having a plurality of connected overlapping annular sections, an outer casing and a noise-suppressing material between the pipe and the outer casing. The casing has a first strip wound helically in a first direction of winding with partial overlap in a first overlap region between adjacent portions of the strips. A curable adhesive is arranged between the adjacent portions in the overlap region to provide a substantially leak proof seal.

BACKGROUND OF THE INVENTION

The present invention relates to an exhaust silencer of the typecomprising an inner, flexible pipe, an outer casing and possibly anoise-suppressing material such as mineral wool, steel wool or the likebetween the pipe and the outer casing.

The known technology, represented by Swedish Patents No. 73 11 076-9 andNo. 85 00 785-4 and British Patent No. 1 191 124, for instance, proposesa flexible or bendable exhaust silencer. The problem with this is thatattempts have been made to furnish the exhaust pipe with two propertieswhich are in opposition to each other. On the one hand the exhaust pipeshall be flexible or bendable while retaining an unrestricted crosssection, and on the other hand the shape obtained during the bendingoperation must be retained after the pipe is fitted, for instance on thelower side of a private car, where the exhaust pipe may be subjected toconsiderable inertial force resulting in unintentional bending. Thealternative is a relatively large number of points for attaching theexhaust pipe to the vehicle.

SUMMARY OF THE INVENTION

An object of the invention is therefore to provide an exhaust pipe ofthe type described in the introduction, by means of which said drawbacksare eliminated.

An exhaust silencer according to the invention is thus of the typecomprising an inner, flexible pipe, an outer casing and possibly anoise-suppressing material between the pipe and the outer casing, theexhaust pipe being characterised in that the casing comprises a stripwound helically with partial overlap, a curable adhesive being arrangedbetween the turns in the overlap region. According to one embodiment asecond strip may be wound helically on the casing, the direction ofwinding being opposite to that of the strip comprising the casing. Thesecond strip may also be wound with partial overlap and a curableadhesive is arranged between the turns, at least in the overlap region.One or both strips may be coated on the inner side with the curableadhesive. The outer strip will then adhere to the outer side of thefirst helically wound inner strip. The curable adhesive may be athermosetting adhesive, allowing stabilization of the casing due to theheat from the exhaust fumes, for instance, when the exhaust pipe isfitted in a motor vehicle. Alternatively the adhesive may be curablewhen subjected to a component of the environment such as air ormoisture, in which case the exhaust pipe is provided immediately aftermanufacture with an air-tight wrapping intended to be removedimmediately before the exhaust pipe is to be fitted, such as when theexhaust pipe is being bent.

The inner pipe may in principle be of any type. However, a pipe formedof relatively short pipe sections jointed by means of upset joints ofball-and-socket type is preferred so that the axial length remainsconstant even when bent. This reduces the risk of gaps appearing betweenthe turns of the casing strip when the pipe is subjected to force suchas axial stretching during bending operations.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, defined in the appended claims will now be described withreference to an embodiment illustrated only schematically in thedrawings, in which:

FIG. 1 shows schematically an axial section through a preferred innerpipe in the exhaust pipe according to the invention, and also suggests amethod of manufacture.

FIG. 2 shows schematically an axial section through an exhaust pipeaccording to the invention.

DETAILED DESCRIPTION

It can be seen that the pipe 2 in FIG. 1 is formed of sheet-metal rings10 consisting generally of cylindrical perforated elements withexternally generally concave cross-sectional profile 5, the sections 6,7 being of different lengths. The perforations 8 serve to facilitatenoise suppression in the exhaust. As indicated in FIG. 1, the largerflange 6 of a ring 10 is fitted the smaller flange 7 onto an adjacentring 10 in the direction of the arrow 11, a radially inwardly directeduppsetting force 12 being applied to the ring flange 6 so that it isshrunk over the flange 7, thus forming a joint 1 of ball-and-sockettype. The upsetting may possibly be arranged to offer predeterminedfriction between adjacent rings 10 so that they remain in the positionobtained at the bending operation.

FIG. 2 shows that the pipe 2 may be provided externally with anoise-suppressing material 3, such as a layer of mineral wool, steelwool or the like.

The pipe 2, with the noise-suppressing material 3 if any, is thenprovided with a casing 4. The casing 4 comprises at least one strip 41wound helically with partial overlap 42 between adjacent turns. Acurable adhesive 43 is also provided in the overlap region between theturns. The strip 41 is preferably coated with curable adhesive 43 overits entire inner side.

The casing 4 may also include a second strip 141 which is wound outsidethe strip 41, with overlap 142 between adjacent turns, a curableadhesive 143 being provided at least in the overlap region in order tobind the winding turns together at curing. The adhesive 143 ispreferably applied across the entire width of the strip 141, so that thestrip 141 will adhere to the first helically wound strip 41.

It will be understood that the inner pipe 2 shown in FIG. 2 can easilybe bent to the desired shape, while retaining an unrestricted crosssection, and without noticeable resistance from the casing 4 ornoise-suppressing material 3. The exhaust pipe can then be permanentlyfixed in the required shape by curing of the adhesive.

To produce an exhaust system for a private car, for instance, an exhaustpipe according to FIG. 2 can be cut to the desired length and then bentto a shape suitable for the make and model of the car. While the exhaustpipe is still in the moulding device, the curable adhesive 43 can behardened and the pre-shaped exhaust pipe can then be fitted inconventional manner. Alternatively, the exhaust pipe shaped in a bendingoperation can be fitted without curing and the adhesive 43, 143 can thenbe cured by the hot exhaust fumes which will then flow through theexhaust system.

However, it is evident that some other type of curable adhesive may alsobe used, such as one which hardens under the influence of a componentfrom the environment, such as moisture from the atmosphere. In thiscase, the exhaust pipe should be provided with an air-tight wrappingafter manufacture, which will prevent the adhesive from hardening untilthe wrapping is intentionally removed at the time the pipe is to begiven the desired shape and fitted.

I claim:
 1. An exhaust silencer comprising an inner, flexible pipecomprising a plurality of connected overlapping annular sections, anouter casing and a noise-suppressing material between the pipe and theouter casing, wherein the casing comprises a first strip wound helicallyin a first direction of winding with partial overlap in a first overlapregion between adjacent portions of the strips, a curable adhesive beingarranged between the adjacent portions in the overlap region to providea substantially leak proof seal.
 2. An exhaust silencer as claimed inclaim 1, wherein a second strip is wound helically on the first strip ina second direction of winding, the second direction of winding beingopposite to that of the first direction.
 3. An exhaust silencer asclaimed in claim 2, wherein the second strip is wound with partialoverlap in a second overlap region between adjacent portions of thesecond strip and a curable adhesive is arranged in the second overlapregion.
 4. An exhaust silencer as claimed in claim 1, wherein the secondstrip has an inner surface having a width and is coated with the curableadhesive over the width of the inner surface.
 5. An exhaust silencer asclaimed in claim 1, wherein the curable adhesive is a thermosettingadhesive.
 6. An exhaust silencer as claimed in claim 1, wherein theadhesive is curable when subjected to an environmental component such asatmospheric moisture, and further comprising an air-tight wrappingaround the outer casing intended to be removed immediately before theexhaust pipe is fitted to a vehicle.